Reference signal configuration method, apparatus, and system

ABSTRACT

The present disclosure provides a method and apparatus for reference signal configuration. The method includes: determining a time domain density of a phase tracking reference signal (PTRS) according to a first modulation and coding scheme (MCS) and correspondence information between MCSs and PTRS time domain densities; determining a frequency domain density of the PTRS according to a first scheduled bandwidth and correspondence information between scheduled bandwidths and PTRS frequency domain densities; and mapping the PTRS to one or more resource elements (REs) according to the time domain density of the PTRS and the frequency domain density of the PTRS when certain conditions are met.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/808,341, filed on Mar. 3, 2020, which is a continuation of U.S.patent application Ser. No. 16/118,657, filed on Aug. 31, 2018, now U.S.Pat. No. 10,727,998, which is a continuation of International PatentApplication No. PCT/CN2017/107135, filed on Oct. 20, 2017. TheInternational Patent application claims priority to Chinese PatentApplication No. 201710011404.4, filed on Jan. 6, 2017. All of theafore-mentioned patent applications are hereby incorporated by referencein their entireties.

TECHNICAL FIELD

Embodiments of the present invention relate to the field ofcommunications technologies, and in particular, to a reference signalconfiguration method, an apparatus, and a system.

BACKGROUND

5G communications systems use higher carrier frequencies (referred to ashigher frequencies) than Long Term Evolution (LTE) systems. Generally a6 GHz frequency or above may be referred to as a high frequency.Frequency bands such as 28 GHz, 38 GHz, and 72 GHz are currentlyresearched, to implement wireless communication with a larger bandwidthand a higher transmission rate. However, a high-frequency system has amore serious intermediate radio frequency distortion, especiallystronger phase noise impact relative to conventional lower-frequencycommunication. In addition, the impact of a Doppler shift and a carrierfrequency offset (CFO) may increase as a frequency increases.

Multiple-input multiple-output-orthogonal frequency divisionmultiplexing (MIMO-OFDM) is used as an example. In consideration ofphase noise and carrier frequency offsets at both a receive end and atransmit end, a receiving expression for an n^(th) receive antenna on ak^(th) subcarrier after fast Fourier transform (FFT) at the receive endis:

$Y_{n}^{k} = {{\sum\limits_{m = 1}^{M}{H_{nm}^{k}\underset{CPE}{\underset{︸}{P_{n}^{r,0}P_{m}^{t,0}}}S_{m}^{k}}} + \underset{ICI}{\underset{︸}{\sum\limits_{m = 1}^{M}{\sum\limits_{i = 0}^{K - 1}{P_{n}^{r,{{({k - i})}K}}H_{nm}^{i}{\sum\limits_{{l = 0},{{{{l \neq i}\&}l} \neq k}}^{K - 1}{P_{m}^{t,{({i - l})}}S_{m}^{l}}}}}}} + {Z_{n}^{k}.}}$

where

${P_{n}^{r,k} = {\frac{1}{K}{\sum\limits_{t = 0}^{K - 1}{e^{j{\theta_{n}^{r}(t)}}e^{j2\pi{{tk}/K}}}}}},{{P_{m}^{t,k} = {\frac{1}{K}{\sum\limits_{t = 0}^{K - 1}{e^{j{\theta_{m}^{t}(t)}}e^{j2\pi{{tk}/K}}}}}};}$

and in this case,

${P_{n}^{r,0} = {\frac{1}{K}{\sum\limits_{t = 0}^{K - 1}e^{j{\theta_{n}^{r}(t)}}}}},{P_{m}^{t,0} = {\frac{1}{K}{\sum\limits_{t = 0}^{K - 1}{e^{j{\theta_{m}^{t}(t)}}.}}}}$

H_(mm) ^(k) indicates a channel from an m^(th) transmit antenna to then^(th) receive antenna on the k^(th) subcarrier, S_(m) ^(k) indicatessent data of the m^(th) antenna on the k^(th) subcarrier, Z_(n) ^(k)indicates noise on the n^(th) receive antenna on the k^(th) subcarrier,P_(n) ^(r,k) indicates a phase offset on the n^(th) receive antenna onthe k^(th) subcarrier that is caused by the phase noise and the CFO atthe receive end, and P_(m) ^(t,k) indicates a phase offset on an m^(th)transmit antenna on the k^(th) subcarrier that is caused by the phasenoise and the CFO at the transmit end. The impact of phase noise on OFDMperformance mainly lies in two aspects: a common phase error (CPE) andinter-carrier interference (ICI), and impact of the CFO on the OFDMperformance mainly lies in the ICI. In an actual system, the ICI hasweaker impact on performance than the CPE. Therefore, usually the CPE ispreferably compensated for in a phase noise compensation solution.

Phase noise is used as an example. As a frequency band increases, aphase noise level decreases by 20*log(f1/f2). A 2 GHz frequency band anda 28 GHz frequency band are used as examples. A phase noise level of the28 GHz frequency band is 23 dB higher than that of the 2 GHz frequencyband. A higher phase noise level indicates stronger common phase error(CPE) impact and a larger phase error caused by a CPE, as shown in FIG.1A to FIG. 1C.

Different subcarriers in a same OFDM symbol are under same impact of aCPE. Phase errors on different subcarriers are different because ofimpact of white Gaussian noise. Therefore, in frequency domain, aplurality of estimated phase noise values are obtained by using aspecific quantity of phase noise reference signals, and the plurality ofestimated phase noise values are averaged to obtain a CPE, to reduce theimpact of the white Gaussian noise to a greatest extent. Theoretically,a larger quantity of phase noise reference signals indicates a betteraveraging effect and a more accurately estimated CPE. In time domain,because phase noise varies discontinuously, and there is no linearrelationship between different symbols, performance is poorer if timedomain pilots are sparser. In addition, a larger quantity of phase noisereference signals indicates more occupied time-frequency resources andhigher overheads. Therefore, a compromise needs to be made betweenperformance and overheads to determine the quantity of phase noisereference signals.

The prior art provides a phase tracking reference signal (the referencesignal may also be referred to as a pilot) design solution, as shown inFIG. 2A-1 , FIG. 2A-2 , FIG. 2B-1 , and FIG. 2B-2 . A demodulationreference signal (DMRS) and a phase compensation reference signal (PCRS)(which may also be referred to as a phase tracking reference signal(PTRS), and the PCRS and the PTRS are not uniformly named in theindustry currently and are collectively referred to as the PTRSsubsequently for ease of description in the present invention) are usedto complete channel estimation, phase noise estimation, and datademodulation together for both uplink and downlink. The DMRS is used forchannel estimation and data demodulation, and the PTRS is used fortracking a residual phase error. There are a plurality of ports for theDMRS and the PTRS. A same antenna port is used for the PTRS and the DMRSin uplink, and a plurality of ports for the DMRS correspond to a samePTRS port in downlink. In time domain, PTRSs are consecutively mapped,to be specific, a PTRS is mapped to each symbol after the DMRS. Infrequency domain, a frequency division manner is used between differentports. A time domain density and a frequency domain density are set tofixed values (an uplink density is 1/96, and a downlink density is1/48). A quantity of reference signals increases as an effectivebandwidth increases. When a data bandwidth is relatively small, thereare a relatively small quantity of reference signals, and when the databandwidth is less than four RBs, no PTRS is mapped, as shown in FIG.2A-1 and FIG. 2A-2 , and also FIG. 2B-1 and FIG. 2B-2 .

In addition, 2-bit and 1-bit downlink control information (DCI) oruplink control information (UCI) are respectively used for downlink anduplink, to indicate PTRS-related configurations. The downlink is used asan example. The 2-bit DCI is used to indicate whether a base station isto send a PTRS and which port is used if the base station is to send thePTRS. Details are shown in Table 1.

TABLE 1 2-bit Configuration Information Bits Configuration information00 Send no PTRS 01 Send a PTRS by using a port 60 10 Send a PTRS byusing a port 61 11 Send a PTRS by using a port 60 and a port 61

The prior art has the following disadvantages: PTRSs are consecutive intime domain, and a frequency division manner is used for a plurality ofports in frequency domain. Also, a time domain density and a frequencydomain density are fixed values, and a relatively large quantity ofsubcarriers are occupied and overheads are relatively high when a databandwidth is large. In addition, the prior art is not flexible becausethe fixed time domain density and the fixed frequency domain density areused for different scenarios such as different phase noise levels anddifferent moving speeds.

SUMMARY

Embodiments of the present invention provide a reference signalconfiguration method. This can reduce resource overheads, is moreflexible, and better fits requirements of different future 5G scenariosin comparison with the prior art.

According to a first aspect, a reference signal configuration method isprovided, including: mapping a phase tracking reference signal (PTRS) toone or more orthogonal frequency division multiplexing (OFDM) symbolsbased on information about a correspondence between the PTRS and one ormore of a modulation and coding scheme (MCS), a subcarrier spacing (SC),and a bandwidth (BW); and sending the one or more OFDM symbols to whichthe PTRS is mapped to a receive device.

In a possible design, the method further includes: determining to mapthe phase tracking reference signal (PTRS) to the one or more OFDMsymbols.

In another possible design, the determining to map the phase trackingreference signal (PTRS) to the one or more OFDM symbols specificallyincludes: when the MCS meets a preset condition, determining to map thePTRS to the one or more OFDM symbols.

In another possible design, the determining to map the PTRS to the oneor more OFDM symbols specifically includes: when the bandwidth meets apreset condition and the MCS meets a preset condition, determining tomap the PTRS to the one or more OFDM symbols.

In another possible design, the method further includes preconfiguringor prestoring information about a correspondence between the SC and/orthe MCS and a PTRS time domain density, where the PTRS time domaindensity is used to indicate that one PTRS is mapped to every severalOFDM symbols in time domain.

In another possible design, a correspondence between the SC and the PTRStime domain density is different SCs correspond to different PTRS timedomain densities, or different SC intervals correspond to different PTRStime domain densities.

In another possible design, a correspondence between the MCS and thePTRS time domain density is different MCSs correspond to different PTRStime domain densities, or different MCS intervals correspond todifferent PTRS time domain densities.

In another possible design, the method further includes: preconfiguringor prestoring a correspondence between the bandwidth and a quantity ofPTRS frequency domains.

In another possible design, the correspondence is: different bandwidthintervals correspond to different quantities of PTRS frequency domains.

In another possible design, the method further includes: preconfiguringor prestoring a correspondence between the bandwidth and a PTRSfrequency domain density, where the PTRS frequency domain density isused to indicate that one PTRS is mapped to every several subcarriers infrequency domain.

In another possible design, the correspondence is: different bandwidthintervals correspond to different PTRS frequency domain densities.

In another possible design, the method further includes: preconfiguringor prestoring a correspondence between the MCS and a quantity of PTRSfrequency domains.

In another possible design, the correspondence is: different MCSintervals correspond to different quantities of PTRS frequency domains.

In another possible design, the method further includes: preconfiguringor prestoring a correspondence between the MCS and a PTRS frequencydomain density.

In another possible design, the correspondence is: different MCSintervals correspond to different quantities of PTRS frequency domains.

In another possible design, the method further includes: preconfiguringor prestoring a correspondence between both the MCS and the bandwidthand a quantity of PTRS frequency domains.

In another possible design, the method further includes: preconfiguringor prestoring a correspondence between both the MCS and the bandwidthand a PTRS frequency domain density.

In another possible design, the one or more OFDM symbols are some or allsymbols of a physical downlink shared channel (PDSCH) or a physicaluplink shared channel (PUSCH).

In another possible design, the receive device is a terminal or a basestation.

According to a second aspect, a reference signal configuration method isprovided, including: receiving one or more OFDM symbols from a transmitdevice; and determining a PTRS from the one or more OFDM symbols basedon information about a correspondence between the PTRS and one or moreof a MCS, a SC, and a BW. In a possible design, the determining a PTRSfrom the one or more OFDM symbols specifically includes obtaining a SCand/or a MCS of a current slot, determining a PTRS time domain densitybased on preconfigured information about a correspondence between the SCand/or the MCS and the PTRS time domain density; and determining atime-frequency location of the PTRS in the one or more OFDM symbolsbased on the PTRS time domain density and a preset rule. For purposes ofclarity, preconfiguring information may relate to the prestoring of theactual information or preconfiguring how the information is to beobtained.

In another possible design, the determining a PTRS from the one or moreOFDM symbols specifically includes: obtaining a bandwidth in a currentnetwork, and determining the time-frequency location of the PTRS in theone or more OFDM symbols based on preconfigured or prestored informationabout a correspondence between the bandwidth and a quantity of PTRSfrequency domains.

In another possible design, the determining a PTRS from the one or moreOFDM symbols specifically includes obtaining a bandwidth in a currentnetwork; and determining the time-frequency location of the PTRS in theone or more OFDM symbols based on preconfigured or prestored informationabout a correspondence between the bandwidth and a PTRS frequency domaindensity.

In another possible design, the determining a PTRS from the one or moreOFDM symbols specifically includes obtaining the MCS of the currentslot, obtaining a bandwidth in a current network, determining a quantityof PTRS frequency domains or a PTRS frequency domain density based on apreconfigured or prestored correspondence between both the MCS and thebandwidth and the quantity of PTRS frequency domains or the PTRSfrequency domain density and determining the time-frequency location ofthe PTRS in the one or more OFDM symbols based on the quantity of PTRSfrequency domains or the PTRS frequency domain density.

In another possible design, the transmit device is a base station or aterminal.

According to a third aspect, an embodiment of the present inventionfurther provides a transmit device, including: a processor, configuredto map a PTRS to one or more OFDM symbols based on information about acorrespondence between the PTRS and one or more of a MCS, a SC, and aBW; and a transceiver, configured to send the one or more OFDM symbolsto which the PTRS is mapped to a receive device.

In a possible design, the processor is further configured to determineto map the PTRS to the one or more OFDM symbols.

In a possible design, the processor is specifically configured to: whenthe MCS meets a preset condition, determine to map the PTRS to the oneor more OFDM symbols.

In another possible design, the processor is specifically configured to:when the bandwidth meets a preset condition and the MCS meets a presetcondition, determine to map the PTRS to the one or more OFDM symbols.

In another possible design, the transmit device further includes amemory, where the memory is configured to prestore information about acorrespondence between the SC and/or the MCS and a PTRS time domaindensity, where the PTRS time domain density is used to indicate that onePTRS is mapped to every several OFDM symbols in time domain.

In another possible design, a correspondence between the SC and the PTRStime domain density is different SCs correspond to different PTRS timedomain densities, or different SC intervals correspond to different PTRStime domain densities.

In another possible design, a correspondence between the MCS and thePTRS time domain density is different MCSs correspond to different PTRStime domain densities, or different MCS intervals correspond todifferent PTRS time domain densities.

In another possible design, the transmit device further includes thememory, and the memory is configured to prestore a correspondencebetween the bandwidth and a quantity of PTRS frequency domains.

In another possible design, the correspondence is: different bandwidthintervals correspond to different quantities of PTRS frequency domains.

In another possible design, the transmit device further includes thememory, and the memory is configured to prestore a correspondencebetween the bandwidth and a PTRS frequency domain density.

In another possible design, the correspondence is: different bandwidthintervals correspond to different PTRS frequency domain densities.

In another possible design, the transmit device further includes thememory, and the memory is configured to prestore a correspondencebetween the MCS and a quantity of PTRS frequency domains.

In another possible design, the transmit device further includes thememory, and the memory is configured to prestore a correspondencebetween the MCS and a PTRS frequency domain density.

In another possible design, the transmit device further includes thememory, and the memory is configured to prestore a correspondencebetween both the MCS and the bandwidth and a quantity of PTRS frequencydomains.

In another possible design, the transmit device further includes thememory, and the memory is configured to prestore a correspondencebetween both the MCS and the bandwidth and a PTRS frequency domaindensity.

In another possible design, the transmit device is a base station or aterminal.

In another possible design, the receive device is a terminal or a basestation.

According to a fourth aspect, an embodiment of the present inventionfurther provides a receive device, including: a transceiver, configuredto receive one or more OFDM symbols from a transmit device; and aprocessor, configured to determine a PTRS from the one or more OFDMsymbols based on information about a correspondence between the PTRS andone or more of a MCS, a SC, and a BW.

In a possible design, the processor is specifically configured to obtaina SC and/or a MCS of a current slot and determine a PTRS time domaindensity based on preconfigured or prestored information about acorrespondence between the SC and/or the MCS and the PTRS time domaindensity, where the PTRS time domain density is used to indicate that onePTRS is mapped to every several OFDM symbols in time domain anddetermine a time-frequency location of the PTRS in the one or more OFDMsymbols based on the PTRS time domain density and a preset rule.

In another possible design, the processor is specifically configured toobtain a bandwidth in a current network and determine the time-frequencylocation of the PTRS in the one or more OFDM symbols based onpreconfigured or prestored information about a correspondence betweenthe bandwidth and a quantity of PTRS frequency domains.

In another possible design, the processor is specifically configured toobtain a bandwidth in a current network and determine the time-frequencylocation of the PTRS in the one or more OFDM symbols based onpreconfigured or prestored information about a correspondence betweenthe bandwidth and a PTRS frequency domain density.

In another possible design, the processor is specifically configured toobtain the MCS of the current slot obtain a bandwidth in a currentnetwork, determine a quantity of PTRS frequency domains or a PTRSfrequency domain density based on a preconfigured or prestoredcorrespondence between both the MCS and the bandwidth and the quantityof PTRS frequency domains or the PTRS frequency domain density, anddetermine the time-frequency location of the PTRS in the one or moreOFDM symbols based on the quantity of PTRS frequency domains or the PTRSfrequency domain density.

In another possible design, the transmit device is a base station or aterminal.

In another possible design, the receive device is a terminal or a basestation.

According to a fifth aspect, an embodiment of the present inventionfurther provides a communications system, including the transmit deviceaccording to the third aspect and/or the receive device according to thefourth aspect.

In the embodiments of the present invention, a correspondence betweenthe PTRS and the subcarrier spacing or the modulation and coding schemeor the bandwidth is used to implicitly indicate the time-frequencylocation of the PTRS. In comparison with the prior art, no explicitindication is required, and signaling overheads are reduced.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention or in the prior art more clearly, the following brieflydescribes the accompanying drawings required for describing theembodiments or the prior art. Apparently, the accompanying drawings inthe following description show merely some embodiments of the presentinvention, and a person of ordinary skill in the art may still deriveother drawings from these accompanying drawings without creativeefforts.

FIG. 1A shows constellation points at which 64QAM (quadrature amplitudemodulation) modulation signal is not affected by phase noise;

FIG. 1B shows constellation points at which 64QAM modulation signal isaffected by phase noise on a 2 GHz frequency band;

FIG. 1C shows constellation points at which 64QAM modulation signal isaffected by phase noise on a 28 GHz frequency band;

FIG. 2A-1 and FIG. 2A-2 are a schematic diagram of an uplink phasetracking pilot solution in the prior art;

FIG. 2B-1 and FIG. 2B-2 are a schematic diagram of a downlink phasetracking pilot solution in the prior art;

FIG. 3 is a schematic diagram of a network architecture according to anembodiment of the present disclosure;

FIG. 4 is a schematic diagram of a reference signal design patternaccording to an embodiment of the present disclosure;

FIG. 5 is a schematic diagram of a reference signal configuration methodaccording to an embodiment of the present disclosure;

FIG. 6A is a schematic diagram of a PTRS time domain mapping accordingto an embodiment of the present disclosure;

FIG. 6B is a schematic diagram of another PTRS time domain mappingaccording to an embodiment of the present disclosure;

FIG. 7A is a schematic diagram of a PTRS frequency domain mappingaccording to an embodiment of the present disclosure;

FIG. 7B is a schematic diagram of another PTRS frequency domain mappingaccording to an embodiment of the present disclosure;

FIG. 7C is a schematic diagram of another PTRS frequency domain mappingaccording to an embodiment of the present disclosure;

FIG. 8 is a schematic structural diagram of a transmit device accordingto an embodiment of the present disclosure; and

FIG. 9 is a schematic structural diagram of a receive device accordingto an embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

FIG. 3 is a schematic architectural diagram of an application scenarioaccording to an embodiment of the present disclosure. A networkarchitecture shown in FIG. 3 mainly includes a base station 31 and aterminal 32. The base station 31 may communicate with the terminal 32 byusing a millimeter-wave band of a low frequency (mainly 6 GHz or below)or a relatively high frequency (6 GHz or above). For example, themillimeter-wave band may be 28 GHz, 38 GHz, or an enhanced bandwidth(E-band) band of a data plane with a relatively small coverage area, forexample, a frequency band of 70 GHz or above. The terminal 32 incoverage of the base station 31 may communicate with the base station 31by using the millimeter-wave band of a low frequency or a relativelyhigh frequency.

The terminal 32 in the present invention may communicate with one ormore core networks by using a radio access network (RAN). The terminal32 may be an access terminal, a subscriber unit, a subscriber station, amobile station, a mobile console, a remote station, a remote terminal, amobile device, a user terminal, a terminal, a wireless communicationsdevice, a user agent, or a user apparatus. The access terminal may be acellular phone, a cordless phone, a Session Initiation Protocol (SIP)phone, a wireless local loop (WLL) station, a personal digital assistant(PDA), a handheld device having a wireless communication function, acomputing device, another processing device connected to a wirelessmodem, an in-vehicle device, a wearable device, a terminal in a 5Gnetwork, or the like.

The base station 31 in the present invention may be a Wireless Fidelity(Wi-Fi) station, an eNodeB in LTE, or a base station in next generationcommunication, for example, a 5G base station gNB, a small cell, a microbase station, or may be a relay node, an access point, an in-vehicledevice, a wearable device, or the like operating on a high frequencyband.

Reference signals designed in the embodiments of the present inventionare shown in FIG. 4 (a horizontal axis indicates time domain, and avertical axis indicates frequency domain). In one transmission slot, aPTRS is mapped to one or more OFDM symbols at a specific time domaindensity and a specific frequency domain density. The PTRS is usuallyused to track a rapid channel change, for example, track changes of acarrier frequency offset (CFO), phase noise (PN), and a Doppler shift.The PTRS usually occupies several subcarriers in frequency domain, andin time domain, may occupy all OFDM symbols to which the PTRS is to bemapped, or occupy some OFDM symbols at a specific interval, or occupysome OFDM symbols according to another rule. The rule may be specifiedin a standard and preconfigured or prestored on a transmit device and areceive device.

Optionally, the OFDM symbols to which the PTRS is to be mapped are allsymbols on a physical downlink shared channel (PDSCH) or a physicaluplink shared channel (PUSCH), or all OFDM symbols except an OFDM symbolto which a DMRS is to be mapped, or may be OFDM symbols occupied byanother control channel. This is not limited in the present invention.

As shown in FIG. 5 , an embodiment of the present invention provides areference signal configuration method. The method includes the followingsteps.

S502. A transmit device maps a PTRS to one or more OFDM symbols based oninformation about a correspondence between the PTRS and one or moreparameters. The parameters include, but are not limited to, a modulationand coding scheme (MCS), a bandwidth (BW), and a subcarrier spacing(SC).

S504. The transmit device sends the one or more OFDM symbols to whichthe PTRS is mapped to a receive device.

S506. The receive device receives the one or more OFDM symbols from thetransmit device, and determines the PTRS from the one or more OFDMsymbols based on the information about the correspondence between thePTRS and the one or more of the MCS, the BW, and the SC.

It should be understood that the transmit device mentioned in thisembodiment of the present invention may be a base station or a terminal.When the transmit device is a base station, the receive device is aterminal; or when the transmit device is a terminal, the receive deviceis a base station.

Optionally, before step S502, the method further includes:

S501: Determine whether to map the phase tracking reference signal(PTRS).

Step S501 of determining whether to map the phase tracking referencesignal (PTRS) specifically includes the following implementations.

In a possible implementation, when the modulation and coding scheme(MCS) meets a preset condition, it is determined to map the phasetracking reference signal (PTRS).

For example, when the MCS is less than a threshold M0, the transmitdevice maps no PTRS; or when the MCS is greater than a threshold M0, thetransmit device maps the phase tracking reference signal to one or moreOFDM symbols. MO indicates a threshold for determining whether to mapthe PTRS, M0 is an integer greater than 0, and a larger MCS indicates ahigher modulation and coding rate.

For example, a value of the modulation and coding scheme (MCS) isreferred to as an MCS index. In LTE, the MCS is used to indicate amodulation order and a bit rate, and one MCS index corresponds to onemodulation order and one bit rate. A 3GPP R14 protocol is used as anexample. One MCS index corresponds to one modulation order and onetransport block size (TBS), and a TBS index is a parameter correspondingto the bit rate, as shown in Table 2.

TABLE 2 3GPP 36.213: Modulation, TBS index and redundancy version tablefor PUSCH MCS Index Modulation Order TBS Index Redundancy VersionI_(MCS) Q′_(m) I_(TBS) rv_(idx) 0 2 0 0 1 2 1 0 2 2 2 0 3 2 3 0 4 2 4 05 2 5 0 6 2 6 0 7 2 7 0 8 2 8 0 9 2 9 0 10 2 10 0 11 4 10 0 12 4 11 0 134 12 0 14 4 13 0 15 4 14 0 16 4 15 0 17 4 16 0 18 4 17 0 19 4 18 0 20 419 0 21 6 19 0 22 6 20 0 23 6 21 0 24 6 22 0 25 6 23 0 26 6 24 0 27 6 250 28 6 26 0 29 reserved 1 30 2 31 3

Therefore, comparison between the MCS and M0 mentioned in thisembodiment of the present invention is actually comparison betweenI_(MCS) and M0 in Table 2, and M0 is an integer greater than 0.

It should be further understood that currently a specific value ofI_(MCS) is not determined in a standard, an I_(MCS) value in the futuremay be different from that in existing LTE (for example, in Table 2). Nolimitation is imposed on the I_(MCS) value in this embodiment of thepresent invention.

In another possible implementation, it may be determined, based on boththe MCS and the bandwidth (BW), whether the phase tracking referencesignal needs to be mapped. For example, when I_(MCS) is less than M0, orwhen I_(MCS) is less than M1 and the BW is less than a preset thresholdB0, the transmit device maps no phase tracking information; otherwise,the transmit device needs to map phase tracking information to one ormore OFDM symbols. MO indicates a first threshold for determiningwhether to map the PTRS, M1 indicates a second threshold for determiningwhether to map the PTRS, and B0 indicates a BW threshold for determiningwhether to map the PTRS.

It should be understood that the thresholds M0, B0, and M1 mentionedabove may be constants as specified in a standard, or may be dynamicallyadjusted. If the thresholds need to be dynamically adjusted, a basestation side may actively initiate a threshold adjustment, or a terminalside may actively initiate an adjustment request.

For example, the base station may use higher layer signaling to instructto adjust the MCS threshold M0, or instruct to adjust the MCS thresholdM1 and the BW threshold B0, to adapt to different scenarios andconditions. For example, the MCS threshold M0, or the MCS threshold M1and the BW threshold B0 are adjusted by using signaling in the followingtwo manners:

In Manner 1, a new MCS threshold M0, or a new MCS threshold M1 and a newBW threshold B0 are directly configured by using higher layer signalingsuch as a radio resource control (RRC) or Media Access Control (MAC)control element (MAC CE).

In Manner 2, a subset that includes a plurality of MCS thresholds isstored at a higher layer. Different MCS subsets represent differentconfiguration solutions. A command for adjusting an MCS threshold upwardor downward by L levels is configured by using higher layer signaling.The MCS threshold is correspondingly increased or decreased by L levelsbased on the command at a physical layer. L is an integer greater thanor equal to 1. It should be understood that in this manner, the higherlayer signaling may include a plurality of bits, one bit is used toindicate whether to increase or decrease the MCS threshold, and theother bits are used to indicate a specific level.

It should be noted that when the preset condition mentioned in theforegoing embodiment is not met, a PTRS-related operation is terminated;or when the preset condition mentioned in the foregoing embodiment ismet, a PTRS time domain density and a PTRS frequency domain density needto be determined based on information provided in the followingembodiment.

For step S502 of mapping a PTRS to one or more OFDM symbols based oninformation about a correspondence between the PTRS and one or more of aMCS, a BW, and a SC, it should be understood that before step S502, thetransmit device needs to preconfigure or prestore the information aboutthe correspondence between the PTRS and the one or more of the MCS, thebandwidth (BW), and the SC.

Specifically, the information about the correspondence between the PTRSand the one or more of the MCS, the BW, and the SC may be directlyspecified in the standard and stored by the transmit device in a memory.Alternatively, before the PTRS is mapped, the transmit devicepreconfigures the information about the correspondence between the PTRSand the one or more of the MCS, the BW, and the SC.

Specifically, the information about the correspondence between the PTRSand the one or more of the MCS, the BW, and the SC includes twodimensions: time domain and frequency domain. The following separatelyprovides descriptions from the two dimensions: time domain and frequencydomain.

Time Domain Solution

In time domain, the PTRS may occupy all OFDM symbols to which the PTRSis to be mapped, or occupy, at a specific interval, some OFDM symbols towhich the PTRS may be mapped, or occupy some OFDM symbols according to apreset rule.

One resource block (RB, including 12 resource elements (RE)) is used asan example. It is assumed that one transmission slot is 14 OFDM symbols(numbered from 0 to 13), and OFDM symbols to which the PTRS may bemapped are numbered from 3 to 13. For example, two specific embodimentsare provided in FIG. 6A and FIG. 6B, and respectively correspond to anexample in which the PTRS is mapped to all the OFDM symbols to which thePTRS may be mapped in time domain and an example in which the PTRSoccupies only about half the OFDM symbols.

The base station preconfigures or prestores a table of a correspondencebetween a time domain density and the SC or the MCS, and then obtainsPTRS time domain density configuration information of a current slotbased on the table and SC information and MCS information of the currentslot. The time domain density is used to indicate that one PTRS ismapped to every several OFDM symbols. For example, if the time domaindensity is ⅓, it indicates that one PTRS is mapped to every three OFDMsymbols, or if the time domain density is ¼, it indicates that one PTRSis mapped to every four OFDM symbols.

In this embodiment of the present invention, the receive device maydetermine the PTRS time domain density based on the SC and/or the MCS,and then obtain the PTRS. In comparison with the prior art, noadditional indication information is required to notify a receive end.

There are a plurality of mapping rules between the PTRS time domaindensity and the SC and/or the MCS. The following provides descriptionsby using a plurality of embodiments.

Embodiment 1: Establish a one-to-one correspondence between subcarrierspacings (SCs) and time domain densities.

Specifically, a larger subcarrier spacing indicates a smaller PTRS timedomain density, and this is represented by Density=1/└SC/SC₀/α₀┘ orDensity=1/┌SC/SC₀/α₀┐. Density indicates the time domain density. Forexample, if a value of Density is ⅓, it indicates that one PTRS ismapped to every three OFDM symbols. SC indicates a current subcarrierspacing, SC₀ is a reference subcarrier spacing, α₀ is a constant, and └┘ and ┌ ┐ respectively indicate rounding down and rounding up.

For example, SC₀=60 k, and α₀=1. When SC=60 k, the PTRS time domaindensity is 1, when SC=120 k, the PTRS time domain density is ½, whenSC=240 k, the PTRS time domain density is ¼, and so on, as shown inTable 3.

TABLE 3 Subcarrier spacing Time domain density  60k 1 120k ½ 240k ¼ 480k⅛

It should be understood that the time domain density is greater than orequal to 1/total quantity of symbols and less than or equal to 1. Whenthe time domain density (Density) is greater than 1, Density is directlyset to 1, to be specific, the PTRS is mapped to all symbols. WhenDensity is less than 1/total quantity of symbols, Density is directlyset to 1/total quantity of symbols, to be specific, the PTRS is mappedto only one of the symbols. Herein the total quantity of symbols is atotal quantity of symbols to which the PTRS may be mapped in one slot.Details are not described repeatedly below.

Further, when the time domain density is less than 1, for example, thetime domain density is ⅕, and there are a total of 10 OFDM symbols, thePTRS needs to be mapped to two OFDM symbols, and the PTRS may be mappedto two of the symbols according to a preset rule. For example, thepreset rule may be mapping the PTRS to first two symbols, or mapping thePTRS to a symbol 4 and a symbol 9, or mapping the PTRS based on analgorithm or a formula.

The preset rule may be prestored on the transmit device and the receivedevice. When obtaining the time domain density, the receive device maydetermine a specific time-frequency location of the PTRS according tothe prestored rule.

Optionally, after a table of a correspondence between the subcarrierspacing and the time domain density is established, the time domaindensity may also be corrected based on the modulation and coding scheme(MCS). Specifically, the time domain density may be adjusted bycorrecting a value of α₀. For example, MCSs may be classified into xlevels, and x is greater than or equal to 1. Each MCS level correspondsto one value of α, as shown in Table 4. In this case, a system mayobtain a PTRS time domain density of the current slot based on thepreset table of the correspondence between the SC and the time domaindensity with reference to the MCS level, as shown in Table 4.

TABLE 4 MCS level 0 1 . . . X MCS interval [MCS₀, MCS₁) [MCS₁, MCS₂) . .. [MCS_(x−1), MCS_(x)) Adjustment factor α₀ α₁ . . . α_(x)

It should be understood that MCS interval classification in Table 4 ismerely an example, and intervals may be (MCS₀, MCS₁], (MCS₁, MCS₂],(MCS₂, MCS₃], and the like. This is not limited in the presentinvention.

A value of the MCS is a positive integer.

In this way, a corrected time domain density is Density=1/┌SC/SC₀/α₀┐,and the value of α₀ is no longer a constant, but corresponds todifferent α₀, α₁, and α_(x) based on different MCS intervals recorded inTable 4. In this case, a final time domain density is related to boththe SC and the MCS.

In the configuration of Embodiment 1, after receiving the one or moreOFDM symbols from the transmit device, the receive device may determinea time-frequency location of the PTRS in the one or more OFDM symbols inthe following manner:

obtaining a subcarrier spacing (SC) and/or a modulation and codingscheme (MCS) of a current slot;

determining the PTRS time domain density based on preconfigured orprestored information about a correspondence between the subcarrierspacing (SC) and/or the modulation and coding scheme (MCS) and the PTRStime domain density, where the PTRS time domain density is used toindicate that one PTRS is mapped to every several OFDM symbols in timedomain; and

determining the time-frequency location of the PTRS in the one or moreOFDM symbols based on the PTRS time domain density and a preset rule.

Embodiment 2: Establish a one-to-one correspondence between time domaindensities and SCs.

Specifically, SCs may be classified into K levels, each levelcorresponds to one SC interval, and a subcarrier spacing intervalcorresponding to a level k is (SC_(k-1), SC_(k)]. In addition, one SClevel corresponds to one time domain density. Table 5 provides aspecific example for SC levels and time domain densities.

TABLE 5 SC level 1 2 3 . . . SC interval <60k [60k, 120k) [120k, 240k) .. . Time domain density 1 ½ ¼ . . .

Optionally, after a table of a correspondence between the SC and thetime domain density is established, the preset table may be correctedbased on the MCS.

Specifically, the time domain density may be adjusted by correcting theSC level. For example, MCSs may be classified into 2*x levels, and eachMCS level corresponds to one SC level correction amount, as shown inTable 6. For example, when a value of the MCS level is 0, the table ofthe correspondence between the SC and the time domain density is notcorrected; or when a value of the MCS level is x, the SC level increasesby x levels; or when a value of the MCS level is −x, the SC leveldecreases by x levels. A larger MCS indicates a larger time domaindensity. In this case, a system may obtain a PTRS time domain density ofthe current slot based on the preset table of the correspondence betweenthe SC and the time domain density with reference to the MCS level, asshown in Table 6.

TABLE 6 MCS level −x . . . 0 1 . . . x MCS [MCS₀, MCS₁) . . . [MCS_(m),MCS_(m +) ₁) [MCS_(m +) ₁, MCS_(m +) ₂) . . . [MCS_(x −1), MCS_(X))interval SC level −y . . . 0 1 . . . y correction amount

For example, based on Table 5, when the SC is 80 k and falls within aninterval [60 k, 120 k), a corresponding time domain density is ½. Withreference to Table 6, when a value of the MCS falls within an interval[MCS_(m+1), MCS_(m+2)), a corresponding SC level correction amount is 1,and it indicates that an original SC level 2 is increased to an SC level3. Based on Table 5, it can be learned that a corrected time domaindensity is ¼.

Optionally, higher layer signaling may also be used to instruct toadjust a correspondence, in a solution, between an MCS level and an MCSinterval corresponding to the MCS level and/or to adjust acorrespondence between an SC level and an SC interval corresponding tothe SC level, to adapt to a new scenario and condition.

For example, quantities or a quantity of levels by which the MCS leveland/or the SC level shown in Table 5 or Table 6 are/is increased ordecreased may be directly adjusted by using higher layer signaling.

In the configuration of Embodiment 2, after receiving the one or moreOFDM symbols from the transmit device, the receive device may determinea time-frequency location of the PTRS in the one or more OFDM symbols inthe following manner:

obtaining a subcarrier spacing (SC) and/or a modulation and codingscheme (MCS) of a current slot;

determining the PTRS time domain density based on preconfigured orprestored information about a correspondence between the subcarrierspacing (SC) and/or the modulation and coding scheme (MCS) and the PTRStime domain density, where the PTRS time domain density is used toindicate that one PTRS is mapped to every several OFDM symbols in timedomain; and

determining the time-frequency location of the PTRS in the one or moreOFDM symbols based on the PTRS time domain density and a preset rule.

Frequency Domain Solution

For mapping of the PTRS in frequency domain, a table of a correspondencebetween the MCS and/or the BW and a quantity of subcarriers to which thePTRS is mapped in each OFDM symbol in frequency domain may beestablished according to a specific criterion, or a table of acorrespondence between the frequency domain density and the MCS and/orthe BW may be established according to a specific criterion. In thisembodiment of the present invention, PTRS frequency domain configurationinformation may be indicated based on the MCS and/or the BW, and noadditional indication information is required to notify a receive end.

There are a plurality of mapping rules between a PTRS frequency domainmapping pattern and the MCS and/or the BW. The following uses aplurality of embodiments for description.

In frequency domain, PTRSs occupy several subcarriers, and the PTRSs areevenly distributed or consecutively distributed on the transmissionbandwidth. One resource block is used as an example. It is assumed thatthe PTRS is mapped to all OFDM symbols (3 to 13) in time domain. FIG.7A, FIG. 7B, and FIG. 7C provide three specific embodiments in whichPTRSs are evenly mapped in frequency domain and are mapped to adjacentsubcarriers.

Embodiment 3: Establish a correspondence between the BW and a quantityof PTRS frequency domains.

For example, a correspondence table may be established according to aspecific criterion, as shown in Table 7.

TABLE 7 BW level 0 1 2 . . . K BW <BW₀ [BW₀, BW₁) [BW₁, BW₂) . . .<BW_(K) Quantity of PTRS P₀ P₁ P₂ . . . P_(K) frequency domains

For example, when the bandwidth falls within an interval [BW₀, BW₁), itcan be learned from Table 7 that the quantity of PTRS frequency domainsis P₁. It is assumed that there are a total of 10 subcarriers infrequency domain, and a value of P₁ is 3, and it indicates that the PTRSoccupies a total of three of the 10 subcarriers in frequency domain. Thethree subcarriers may be selected according to a preset rule. Forexample, the preset rule is selecting first three subcarriers, selectinglast three subcarriers, selecting three of the subcarriers based on aformula or an algorithm, or mapping PTRSs to three of the 10 subcarriersat equal intervals.

The preset rule may be specified in the standard and preconfigured orprestored on the transmit device and the receive device.

In the configuration of Embodiment 3, after receiving the one or moreOFDM symbols from the transmit device, the receive device may determinea time-frequency location of the PTRS in the one or more OFDM symbols inthe following manner:

obtaining a bandwidth in a current network; and

determining the time-frequency location of the PTRS in the one or moreOFDM symbols based on preconfigured or prestored information about acorrespondence between the bandwidth and the quantity of PTRS frequencydomains.

Embodiment 4: Establish a correspondence between the BW and a PTRSfrequency domain density T.

The frequency domain density is used to indicate a PTRS density or thequantity of PTRS frequency domains on each scheduled bandwidth.

For example, a correspondence table is established according to aspecific criterion, as shown in Table 8. For example, if the frequencydomain density is equal to 1/12, and the scheduled bandwidth is four RBs(the scheduled bandwidth is a known bandwidth allocated by the basestation to the terminal), that is, 48 subcarriers (each RB includes 12subcarriers), a total of four PTRSs (48* 1/12=4) are mapped on thescheduled bandwidth of four RBs. The four PTRSs may be mapped on thescheduled bandwidth at equal intervals, or may be mapped to fourconsecutive subcarriers, or may be mapped to four inconsecutivesubcarriers through hashing according to another rule. Details are shownin Table 8.

TABLE 8 BW level 0 1 2 . . . K BW interval <BW₀ [BW₀, BW₁) [BW₁, BW₂) .. . <BW_(K) Frequency domain T₀ T₁ T₂ . . . T_(k) density

Optionally, higher layer signaling may be used to instruct to adjust acorrespondence, in a solution, between a BW level and a BW intervalcorresponding to the BW level. Specifically, the BW level may bedirectly increased or decreased by x levels through adjustment by usinghigher layer signaling, where x is an integer less than or equal to K.

In the configuration of Embodiment 4, after receiving the one or moreOFDM symbols from the transmit device, the receive device may determinea time-frequency location of the PTRS in the one or more OFDM symbols inthe following manner obtaining a bandwidth in a current network anddetermining the time-frequency location of the PTRS in the one or moreOFDM symbols based on preconfigured or prestored information about acorrespondence between the bandwidth and the PTRS frequency domaindensity.

Embodiment 5: Establish a one-to-one correspondence between both MCSsand BWs and quantities (K) of frequency domain pilots or frequencydomain densities.

For example, BWs are classified into K levels (columns in Table 9), andMCSs are classified into M levels (rows in Table 9), to obtain acorrespondence table of K*M dimensions, as shown in Table 9.

TABLE 9 BW/MCS BW level 0 1 2 . . . K − 1 MCS level MCS BW <BW₀ [BW₀,[BW₁, . . . >=BW_(k − 1) BW₁) BW₂) 0 <MCS₀ T₁₁ T₁₂ T₁₃ . . . T_(1K) 1[MCS₀, MCS₁) T₂₁ T₂₂ T₂₃ . . . T_(2K) . . . . . . . . . . . . . . . . .. . . . M − 1 >=MCS_(m − 1) T_(M1) T_(M2) T_(M3) . . . T_(MK)

For example, the scheduled bandwidth (BW) allocated by the base stationto the terminal falls within an interval [BW₁, BW₂), and a value of theMCS used by the base station falls within an interval [MCS₀, MCS₁). Itcan be learned, based on mapping information in Table 9, that thequantity of PTRS frequency domains or the PTRS frequency domain densityis T₂₃. T₂₃ herein may be a decimal or an integer.

If T₂₃ indicates the quantity of PTRS frequency domains, an integerobtained after T₂₃ is rounded up or rounded down indicates the quantityof PTRS frequency domains.

If T₂₃ indicates the PTRS frequency domain density, T₂₃ may not berounded.

Further, when T₂₃ indicates the quantity of PTRS frequency domains, thereceive device may determine, according to a preset rule or a presetalgorithm, a specific subcarrier to which the PTRS is mapped.

For example, the preset rule may be mapping T₂₃ PTRSs at equal intervalsstarting from a first subcarrier, or consecutively mapping T₂₃ PTRSsstarting from a fifth subcarrier, or mapping one PTRS every othersubcarrier starting from a first subcarrier until all PTRSs are mapped.

The preset rule or the preset algorithm may be directly specified in thestandard and prestored or preconfigured on the transmit device and thereceive device.

Optionally, higher layer signaling may be used to instruct to adjust acorrespondence, in a solution, between a BW level and a BW intervalcorresponding to the BW level, or instruct to adjust a correspondence,in a solution, between an MCS level and an MCS interval corresponding tothe MCS level, or instruct to adjust both a correspondence between a BWlevel and a BW interval corresponding to the BW level and acorrespondence between an MCS level and an MCS interval corresponding tothe MCS level. The BW level and/or the MCS level may be directlyincreased or decreased by X or Y levels through configuration by usinghigher layer signaling. X and Y are integers greater than 0.

In the configuration of Embodiment 5, after receiving the one or moreOFDM symbols from the transmit device, the receive device may determinea time-frequency location of the PTRS in the one or more OFDM symbols inthe following manner obtain a modulation and coding scheme (MCS) in acurrent network, obtain a bandwidth in the current network, determine aquantity of PTRS frequency domains or a PTRS frequency domain densitybased on a preconfigured or prestored correspondence between both theMCS and the bandwidth and the quantity of PTRS frequency domains or thePTRS frequency domain density, and determine the time-frequency locationof the PTRS in the one or more OFDM symbols based on the quantity ofPTRS frequency domains or the PTRS frequency domain density.

According to the method in the present invention, the receive device mayobtain PTRS-related configuration information by using information suchas the MCS, the BW, and the SC. This can reduce signaling overheads incomparison with the prior art.

FIG. 8 is a schematic block diagram of a transmit device 800 accordingto another embodiment of the present invention. The transmit device 800includes a processor 810, a memory 820, a transceiver 830, an antenna840, a bus 850, and a user interface 860.

Specifically, the processor 810 controls an operation of the transmitdevice 800, and the processor may be a general-purpose processor, adigital signal processor, a dedicated integrated circuit, a fieldprogrammable gate array, or another programmable logic device.

The transceiver 830 includes a transmitter 832 and a receiver 834, thetransmitter 832 is configured to transmit a signal, and the receiver 834is configured to receive a signal. There may be one or more antennas840. The transmit device 800 may further include the user interface 860such as a keyboard, a microphone, a loudspeaker, and/or a touchscreen.The user interface 860 may transfer content and a control operation tothe transmit device 800.

All components of the transmit device 800 are coupled together by usingthe bus 850. In addition to a data bus, the bus 850 includes a powerbus, a control bus, and a status signal bus. However, for clarity ofdescription, various buses are marked as the bus 850 in the figure. Itshould be noted that the foregoing descriptions about the transmitdevice structure may be applied to the embodiments of the presentinvention.

The memory 820 may include a read-only memory (ROM), a random accessmemory (RAM), or another type of dynamic storage device that may storeinformation and an instruction, or may be a magnetic disk storage. Thememory 820 may be configured to store an instruction for implementingthe related method provided in the embodiments of the present invention.It may be understood that an executable instruction is programmed orloaded into at least one of the processor 810, a cache, and a long termmemory of the transmit device 800.

In a specific embodiment, the processor 810 is configured to map a PTRSto one or more OFDM symbols based on information about a correspondencebetween the PTRS and one or more of a modulation and coding scheme(MCS), a bandwidth (BW), and a subcarrier spacing (SC).

The transceiver 830 is configured to send the one or more OFDM symbolsto which the PTRS is mapped to a receive device.

Optionally, the processor 810 is further configured to determine to mapthe phase tracking reference signal (PTRS) to the one or more orthogonalfrequency division multiplexing (OFDM) symbols.

Further, the processor 810 is specifically configured to: when the MCSmeets a preset condition, determine to map the PTRS to the one or moreOFDM symbols.

Further, the processor 810 is specifically configured to, when thebandwidth meets a preset condition and the MCS meets a preset condition,determine to map the PTRS to the one or more OFDM symbols.

Optionally, the memory 820 is configured to prestore information about acorrespondence between the subcarrier spacing and/or the MCS and a PTRStime domain density, where the PTRS time domain density is used toindicate that one PTRS is mapped to every several OFDM symbols. For aspecific correspondence, refer to the descriptions in Embodiment 1 andEmbodiment 2, and details are not described herein again.

Optionally, the memory 820 is configured to prestore a correspondencebetween the bandwidth and a quantity of PTRS frequency domains or a PTRSfrequency domain density.

Optionally, the memory 820 is configured to prestore a correspondencebetween the MCS and a quantity of PTRS frequency domains or a PTRSfrequency domain density.

Optionally, the memory 820 is configured to prestore a correspondencebetween both the MCS and the bandwidth and a quantity of PTRS frequencydomains or a PTRS frequency domain density.

It should be understood that the transmit device shown in FIG. 8 may bea base station or a terminal.

It should be further understood that the transmit device shown in FIG. 8corresponds to the transmit device in the foregoing method embodiment,and descriptions about all details of the method embodiment may be usedto explain the apparatus embodiment of the transmit device. For detailsof interaction between the transmit device and the receive device, referto the foregoing description. Details are not described again.

FIG. 9 is a schematic block diagram of a receive device 900 according toanother embodiment of the present invention. The receive device 900includes a processor 910, a memory 920, a transceiver 930, an antenna940, a bus 950, and a user interface 960.

Specifically, the processor 910 controls an operation of the receivedevice 900, and the processor may be a general-purpose processor, adigital signal processor, a dedicated integrated circuit, a fieldprogrammable gate array, or another programmable logic device.

The transceiver 930 includes a transmitter 932 and a receiver 934, thetransmitter 932 is configured to transmit a signal, and the receiver 934is configured to receive a signal. There may be one or more antennas940. The receive device 900 may further include the user interface 960such as a keyboard, a microphone, a loudspeaker, and/or a touchscreen.The user interface 960 may transfer content and a control operation tothe receive device 900.

All components of the receive device 900 are coupled together by usingthe bus 950. In addition to a data bus, the bus 950 includes a powerbus, a control bus, and a status signal bus. However, for clarity ofdescription, various buses are marked as the bus 950 in the figure. Itshould be noted that the foregoing descriptions about a network elementstructure may be applied to the embodiments of the present invention.

The memory 920 may include a read-only memory (ROM), a random accessmemory (RAM), or another type of dynamic storage device that may storeinformation and an instruction, or may be a magnetic disk storage. Thememory 920 may be configured to store an instruction for implementingthe related method provided in the embodiments of the present invention.It may be understood that an executable instruction is programmed orloaded into at least one of the processor 910, a cache, and a long termmemory of the receive device 900. In a specific embodiment, the memoryis configured to store computer executable program code. When theprogram code includes an instruction, and the processor executes theinstruction, the instruction enables the receive device to perform thefollowing operations:

The transceiver 930 is configured to receive one or more orthogonalfrequency division multiplexing OFDM symbols from a transmit device.

The processor 910 is configured to determine a phase tracking referencesignal (PTRS) from the one or more OFDM symbols based on informationabout a correspondence between the PTRS and one or more of a modulationand coding scheme (MCS), a bandwidth (BW), and a subcarrier spacing(SC).

Optionally, the processor 910 is specifically configured to obtain asubcarrier spacing (SC) and/or a modulation and coding scheme (MCS) of acurrent slot determine a PTRS time domain density based on preconfiguredor prestored information about a correspondence between the subcarrierspacing and/or the MCS and the PTRS time domain density, where the PTRStime domain density is used to indicate that one PTRS is mapped to everyseveral OFDM symbols in time domain; and determine a time-frequencylocation of the PTRS in the one or more OFDM symbols based on the PTRStime domain density and a preset rule.

Optionally, the processor 910 is specifically configured to obtain abandwidth in a current network; and determine the time-frequencylocation of the PTRS in the one or more OFDM symbols based onpreconfigured or prestored information about a correspondence betweenthe bandwidth and a quantity of PTRS frequency domains.

Optionally, the memory 920 is configured to prestore information about acorrespondence between the subcarrier spacing or the MCS and a PTRS timedomain density, where the PTRS time domain density is used to indicatethat one PTRS is mapped to every several OFDM symbols.

Optionally, the processor 910 can be configured to obtain a bandwidth ina current network and determine the time-frequency location of the PTRSin the one or more OFDM symbols based on preconfigured or prestoredinformation about a correspondence between the bandwidth and a PTRSfrequency domain density.

Optionally, the processor 910 is configured to obtain a modulation andcoding scheme (MCS) in a current network, obtain a bandwidth in thecurrent network, determine a quantity of PTRS frequency domains or aPTRS frequency domain density based on a preconfigured or prestoredcorrespondence between both the modulation and coding scheme (MCS) andthe bandwidth and the quantity of PTRS frequency domains or the PTRSfrequency domain density; and determine the time-frequency location ofthe PTRS in the one or more OFDM symbols based on the quantity of PTRSfrequency domains or the PTRS frequency domain density.

Optionally, the memory 920 is configured to prestore a correspondencebetween the bandwidth and a quantity of PTRS frequency domains or a PTRSfrequency domain density.

Optionally, the memory 920 is configured to prestore a correspondencebetween the MCS and a quantity of PTRS frequency domains or a PTRSfrequency domain density.

Optionally, the memory 920 is further configured to prestore acorrespondence between both the modulation and coding scheme (MCS) andthe BW and a quantity of PTRS frequency domains.

Optionally, the memory 920 is further configured to prestore acorrespondence between both the MCS and the BW and a PTRS frequencydomain density.

For a specific implementation of performing operations by the processorincluded in the receive device, refer to corresponding steps performedby the receive device in the method embodiment. Details are notdescribed again in this embodiment of the present invention.

It should be understood that the receive device shown in FIG. 9corresponds to the receive device in the foregoing method embodiment,and descriptions about all details of the method embodiment may be usedto explain the apparatus embodiment of the receive device. For detailsof interaction between the transmit device and the receive device, referto the foregoing description. Details are not described again.

An embodiment of the present invention further provides a computerstorage medium, configured to store a computer software instruction usedby a transmit device. The computer software instruction includes aprogram designed for performing the foregoing embodiment.

An embodiment of the present invention further provides a computerstorage medium, configured to store a computer software instruction usedby the foregoing receive device. The computer software instructionincludes a program designed for performing the foregoing embodiment.

An embodiment of the present invention further provides a communicationsnetwork system, including a transmit device and a receive device.

The transmit device is configured to perform steps performed by thetransmit device in the method embodiment.

The receive device is configured to perform steps performed by thereceive device in the method embodiment.

For a process of interaction between the transmit device and the receivedevice, refer to the descriptions in the method embodiment, and detailsare not described herein again.

In the embodiments of the present invention, the subcarrier spacing orthe modulation and coding scheme or the bandwidth is used to implicitlyindicate the time-frequency location of the PTRS, so that no explicitDCI indication is required. In comparison with the prior art, signalingoverheads are reduced.

In the specification, claims, and accompanying drawings of the presentinvention, the terms “first”, “second”, “third”, “fourth”, and the likeare intended to distinguish between different objects but do notindicate a particular order. Moreover, the terms “include”, “contain”,and any other variant thereof are intended to cover a non-exclusiveinclusion. For example, a process, a method, a system, a product, or adevice that includes a series of steps or units is not limited to thelisted steps or units, but optionally further includes an unlisted stepor unit, or optionally further includes another inherent step or unit ofthe process, the method, the system, the product, or the device.

All or some of the foregoing embodiments may be implemented by usingsoftware, hardware, firmware, or any combination thereof. When softwareis used to implement the embodiments, all or some of the embodiments maybe implemented in a form of a computer program product. The computerprogram product includes one or more computer instructions. When thecomputer program instructions are loaded and executed on a computer, theprocedures or functions according to the embodiments of the presentinvention are all or partially generated. The computer may be ageneral-purpose computer, a dedicated computer, a computer network, oranother programmable apparatus. The computer instructions may be storedin a computer-readable storage medium or may be transmitted from acomputer-readable storage medium to another computer-readable storagemedium. For example, the computer instructions may be transmitted from awebsite, computer, server, or data center to another website, computer,server, or data center in a wired (for example, a coaxial cable, anoptical fiber, or a digital subscriber line (DSL)) or wireless (forexample, infrared, radio, or microwave) manner. The computer-readablestorage medium may be any usable medium accessible by the computer, or adata storage device, such as a server or a data center, integrating oneor more usable media. The usable medium may be a magnetic medium (forexample, a floppy disk, a hard disk, or a magnetic tape), an opticalmedium (for example, a DVD), a semiconductor medium (for example, asolid state disk (SSD)), or the like.

What are disclosed above are merely examples of the embodiments of thepresent invention, and certainly are not intended to limit the scope ofthe claims of the present invention. Therefore, equivalent variationsmade in accordance with the claims of the present invention shall fallwithin the scope of the present invention.

What is claimed is:
 1. A reference signal transmission method performedby a transmit device, comprising: determining a time domain density of aphase tracking reference signal (PTRS) based on a modulation and codingscheme (MCS) and a correspondence between MCS and PTRS time domaindensity; determining a frequency domain density of the PTRS based on ascheduled bandwidth and a correspondence between scheduled bandwidth andPTRS frequency domain density; mapping the PTRS to one or moreorthogonal frequency division multiplexing (OFDM) symbols according tothe time domain density of the PTRS and the frequency domain density ofthe PTRS; and sending the PTRS which is mapped to the one or more OFDMsymbols to a receive device; wherein the correspondence between MCS andPTRS time domain density comprises: different MCS intervals one-to-onecorresponding to different PTRS time domain densities; wherein thecorrespondence between scheduled bandwidth and PTRS frequency domaindensity comprises: different scheduled bandwidth intervals one-to-onecorresponding to different PTRS frequency domain densities.
 2. Themethod according to claim 1, further comprising: when the MCS is lessthan a first threshold, not mapping the PTRS; or when the scheduledbandwidth is less than a second threshold, not mapping the PTRS.
 3. Themethod according to claim 2, further comprising: receiving the first orthe second threshold through a higher layer signaling.
 4. The methodaccording to claim 1, wherein: the correspondence between MCS and PTRStime domain density and the correspondence between scheduled bandwidthand PTRS frequency domain density are preconfigured or prestored.
 5. Acommunications apparatus, comprising: a processor, configured todetermine a time domain density of a phase tracking reference signal(PTRS) based on a modulation and coding scheme (MCS) and acorrespondence between MCS and PTRS time domain density; determine afrequency domain density of the PTRS based on a scheduled bandwidth anda correspondence between scheduled bandwidth and PTRS frequency domaindensity; and map the PTRS to one or more orthogonal frequency divisionmultiplexing (OFDM) symbols according to the time domain density of thePTRS and the frequency domain density of the PTRS; and a transceiver,configured to send the PTRS which is mapped to the one or more OFDMsymbols to a receive device; wherein the correspondence between MCS andPTRS time domain density comprises: different MCS intervals one-to-onecorresponding to different PTRS time domain densities; wherein thecorrespondence between scheduled bandwidth and PTRS frequency domaindensity comprises: different scheduled bandwidth intervals one-to-onecorresponding to different PTRS frequency domain densities.
 6. Thecommunications apparatus according to claim 5, further comprising: whenthe MCS is less than a first threshold, not mapping the PTRS; or whenthe scheduled bandwidth is less than a second threshold, not mapping thePTRS.
 7. The communications apparatus according to claim 6, wherein: thetransceiver is further configured to receive the first or the secondthreshold through a higher layer signaling.
 8. The communicationsapparatus according to claim 5, further comprising: a memory, configuredto store the correspondence between MCS and PTRS time domain density andthe correspondence between scheduled bandwidth and PTRS frequency domaindensity.
 9. The communications apparatus according to claim 5, wherein:the processor is further configured to preconfigure the correspondencebetween MCS and PTRS time domain density and the correspondence betweenscheduled bandwidth and PTRS frequency domain density.
 10. Thecommunications apparatus according to claim 5, wherein: thecorrespondence between MCS and PTRS time domain density and thecorrespondence between scheduled bandwidth and PTRS frequency domaindensity are preconfigured or prestored.